1. Field of Invention
The invention pertains to the field of signal transmission. More particularly, the invention pertains to transmissions between components of a scanning device and a method using paired differential analog signals for the same.
2. Description of Related Art
The scanner is a device having functions disposed between copy machines and cameras. Scanners used to be expensive, and were almost exclusively used by specialists. Recently, due to the advancement in technology, coupled with market competition, the price of scanners has dropped. In fact, scanners have moved into the mainstream of personal computer peripherals.
Scanners can be divided into various categories either according to their sale price or function. Ordinarily, the scanner categories include handheld scanners, paper feeding scanners, card scanners, negative scanners, and the flat panel scanners, etc. Out of the above categories, the flat panel scanner is the most popular. The flat panel scanner is analogous to a flat glass panel. Texts or graphics are placed on top of the flat glass panel, the content of which is read by sensor. Because of simplicity of structure and ease of usage, coupled with the fact that it is highly expandable, flat panel scanners have moved into the mainstream of personal computer industry.
Currently, because the computer interface possesses an ever-increasing speed, scanners need to possess compatible data processing speeds as well. The increased speed results in undesirable electro-magnetic interference (EMI) which is generated as a concomitant of the increased speed.
Referring to FIG. 1, a commonly known prior art scanning device 10 is shown. The scanning device 10 includes an image capturing board 102 and a mainboard 104. By way of example, the image capturing board 102 may be a charge coupled device (CCD) board. A cable couples the image capturing board 102 to mainboard 104.
The above mentioned image capturing board 102 includes an image capturing device 106 which may be CCD. The above mentioned mainboard 104 includes an analog front-end 108 (AFE), analog to digital converter 110, and clock generator 112.
The operation of device 10 is described as follows. Initially, a clock generator 112 of the image capture device 104 generates a clock signal, which is applied to the image capture component 106. This way, the image capture component 106 is driven. Consequently, the image capture component 106 transforms an optic data signal that was captured into an analog electronic signal. At this juncture, the analog front-end 108 transforms the analog electronic signal into an analog front-end electronic signal. The analog front-end electronic signal is subject to an A/D converter 110, wherein the analog front-end electronic signal is converted into a digital signal, and the digital signal is output. But it should be noted that clock generator 112 includes high frequency signals such as shift clock signals (φ1, φ2), which are a pair of opposite phase signals. Opposite phase will be defined infra. It is known that opposite phase signals' electromagnetic interference cancel each other. However, in scanner technology, no known electronic signal transmission uses single end mode transmission.
Referring to FIG. 2, the wave shape of a commonly known electronic signal Vl under single end mode transmission is shown. As can be appreciated, analog signal Vl has a potential level Vos. Typically the electromagnetic interference is in direct proportion to signal potential level, frequency, and transmission distance. Because signal Vl possesses high potential Vos as well as relatively high frequency and long transmission lines, the single end mode transmission can increase the electro-magnetic interference. Therefore, electro-magnetic interference can cause problems that are undesirable. Because the electro-magnetic interference can cause health problems, various jurisdictions have established standards with regard to the same. Therefore, how to reduce a scanning device's electro-magnetic interference so as to comport with the standards is important.
Therefore it is important to provide a scanning method and device wherein actual magnetic interference is reduced.